Nanomateriais semicondutores aplicados na fabricação de dispositivos eletroquímicos

Abstract

This dissertation was subdivided into 3 different studies. In the first study, it was proposed the development of a photo-electrochemical system for the removal of caffeine in natural water samples. Photo-anodes made with bismuth vanadate (BiVO4) modified with reduced graphene oxide were developed and characterized. The number of layers deposited in the photo-anode, the potential difference applied in the photo-electrochemical system, the power, the wavelength and the positioning of the irradiated light were evaluated by linear scanning voltammetry. Finally, the proposed system promoted a removal of up to 99.1% for caffeine after 6 hours of photo-electrocatalytic treatment under pseudo first order kinetics. In the second study, a photo-electrochemical sensor was developed for the detection of dopamine through immobilization of bismuth vanadate and graphene quantum dots (GQDs) on a fluoride-doped tin oxide (FTO) electrode. The electrochemical and photo-electrochemical behavior of BiVO4/GQDs was studied using linear scanning voltammetry in a system with on/off lighting and electrochemical impedance spectroscopy under visible light irradiation. The analytical performance of the sensor was studied in the concentration range between 3.6 × 10-8 and 2.5 × 10-4 mol L-1. A limit of detection of 8.2 × 10-9 mol L-1 and a limit of quantification of 2.7 × 10-8 mol L-1 was estimated. The selectivity of the sensor was evaluated in the presence of ascorbic and uric acid in concentration values up to 10 and 100 times higher, respectively. Therefore, this sensor had potential to be applied in the monitoring of free dopamine in the urine of humans. In a third study, a method was developed for the simultaneous quantification of diclofenac, acetaminophen and caffeine in lake water samples, using a chemically modified voltammetric sensor with reduced graphene oxide (RGO) and silver nanoparticles ( AgNPs). For the simultaneous detection of these endocrine disruptors, the differential pulse voltammetry technique was used. A linear response of the current signals as a function of the endocrine disruptors concentration was obtained with detection limits in the order of 10-7 mol L-1, thus presenting potential to be applied in effluent treatment plants and in the online monitoring of the photo-electro-degradation process of environmental contaminants.